Organic coatings provide one of the most cost effective means for corrosion protection of structural alloys and are used extensively in both commercial and military applications. The patent to Saeki, et al U.S. Pat. No. 4,959,277 discloses one method of using organic coating over steel to prevent corrosion. Various acrylic and other resin films are disclosed for use over zinc-coated steel. Saeki does not disclose the addition of cations in the organic phase to inhibit disbonding. Anticipated changes in coating technology brought about by environmental concerns for excessive volatile organic content of paints require rapid assessment of coatings to replace environmentally hazardous systems. Simplifying coating processes by eliminating surface conversion layers now required for adhesion of paints to steel would provide a benefit to manufacturing and structural maintenance. A critical need exists, therefore, to prolong the life of organic coatings on steel in a corrosive environment. The patent to Shyu U.S. Pat. No. 4,962,004 discloses the use of ammonium ions on a small scale to inhibit electochemical reduction of a polymide during an electoplating process. Shyu is directed to adding ammonium ions to the electoplating solution for a circuit board which includes gold and does not contemplate using a high molecular weight quaternay ammonium compound as in addition to an organic phase polymer for preventing disbonding of a polymer-steel interface. Shyu does not contemplate the use of his invention for large structural items envisioned as by the present invention.
Although the barrier nature of organic coatings plays a role in protecting the steel substrate, it must be recognized that adhesion and molecular blocking of active sites on the surface are crucial for providing corrosion resistance, and may actually determine the ultimate life of the coating system. The concept of the paint film as an impermeable membrane is largely discredited by permeability data for water and oxygen. Clearly, adhesion or maintenance of an intimate molecular contact between a low dielectric constant, non-conducting organic material and a metal substrate diminishes the rate of corrosion of the metal despite the apparent facility of corrodents such as oxygen and ionic solutes to permeate the organic matrix.